Method of securing fins to tubes



Nov. 9, 1965 c, KURTZ ETAL 3,216,095

METHOD OF SECURING FINS TO TUBES Filed Feb.' 15, 1962 passageway within the tubular member.

United States Patent 3,216,095 METHOD OF SECURING FINS T0 TUBES Orville C. Kurtz and Harold G. Thompson, Wellsville, N.Y., assignors, by mesne assignments, to The Air Preheater Company, Inc., a corporation of Delaware Filed Feb. 16, 1962, Ser. No. 173,787 2 Claims. '(Cl. 29--157.3)

This invention relates to heat exchange apparatus and particularly to a tube type heat exchanger and a method of tightly securing a series of extended surface fins thereto.

I Fins or extended surface means have long been variously secured. to tube type heat exchange elements to facilitate the transfer of heat between a fluid flowing through a passageway within the tube and a fluid flowing over the fins outside the tube. Such fins perform their intended function most efliciently when they tightly embrace the tubes through which the fluid is being directed, and to secure the desired fitting, thin fins are usually crimped or soldered to a central tube, or a flexible central tube is expanded into a tight fit with its surrounding fins in order that the best possible connection be obtained.

For heat exchange equipment adapted for use in the handling of large volumes of fluid in a corrosive atmos-- phere, especially where long equipment life and a high rate'of heat transfer is required, the usual heat exchange fins formed of thin metallic sheet are not adequate and the use of large capacity pipe with comparably heavy fins becomes mandatory.

Thus it is not unusual for heat exchange fins for such applications be formed of /g steel plate while the fluid carrying pipe is comprised of a heavy 4" steel pipe.

The fins are commonly welded individually to the pipe to provide a good bond therebetween that readily transmits heat between the spaced fluids. It is apparent that the fabricator of such heavy stock into an effective heat exchanger may present many problems not associated with the fabrication of the usual light gauge material. Thus this invention has as its chief object to provide a method of producing a heavy duty fin tube arrangement that is both eflicient and rug'gedly strong.

Still further and more detailed objects of the invention will become more apparent when viewed in conjunction with the accompanying drawing in which the single figure is a perspective view of a fin tube heat exchange element, assembled according to the present invention.

Referring to the drawing, reference numeral 12 desigplication of a force F to opposite sides of the fin in a direction generally normal to the slot 18 will tend to close the slot and reduce the diameter of the aperture 16. As the diameter of the aperture is reduced, the annular surface of the aperture embraces the outer surface of the tubular member to hold the fin in any predetermined position with respect to the tubular member 12.

The manner in which or the means by which the required transverse force is applied to each fin to close its radial slot is of no particular significance as long as the force is applied generally normal to the slot. Thus apparatus devised to clamp a single or multiple fin assembly may be used selectively without altering the basic concept of the invention.

During the period in which the slot 18 is compressed and the surface of aperture 16 is held in close contact with the outer surface of the tubular member 12, the slot is welded shut with a metallic weld 22 that locks the aperture of the fin tightly about the tubular member. As I the weld in the slot cools, it solidifies, grips the sides of the slot and contracts to decrease the diameter of the aperture and cause the inner surface of the aperture to grip more firmly the outer surface of tube 12 whereby the fin is in effect locked even more firmly in its predetermined position on the tube.

Fin members thus connected to a central tubular member are mechanically independent. However, they are frictionally held so tightly that the transfer of heat between a fluid flowing through the tubular member and a fluid flow-ing across the fins attains a consistently high the steps of forming an opening in said fin slightly larger nates ametallic tubular member provided with a series of longitudinally spaced extended surface fins 14 over which one fluid is adapted to flow in heat exchange relation with a second fluid which is directed through the Each fin 14 comprises essentially a plane metallic sheet having a central aperture 16 formed :with a diameter slightly greater than the diameter of the tubular'member 12 around which it is adapted to extend. Each extended surface fin 14 is provided with a single radial slot 18 that extends from its central aperture to its outer periphcry. The width w'-of each-slo.t,thus formed is of greater extent than the difference between the circumference of the aperture 16 inthe fin 14 andthe: outside circumference of the tubular member 12 Thus the apthan the outer dimensions of said tubular member, forming a radial slot in said fin extending from said opening to its outer periphery, inserting said tubular member into the opening in said extended surface, exerting a force on said fin tending to close the slot and simultaneously filling each slot with a molten metallic material that bonds itself to the spaced edges of said slot and upon.

cooling solidifies and contracts to draw the edges of said slot into a mutually closer relationship whereby the opening in said tin tightly embraces the outer surface of the tubular member.

2. The method of firmly securing a transverse extended surface fin to the outer surface of a tubular member comprising the steps of forming an opening in said fin with a diameter greater than the outside diameter of said tubular member, forming a radial slot in said fin with a transverse width greater than the difference between the circumference of the opening in said fin and that of the outer surface of said tubular member, fitting said fin around said tubular member according to a predetermined arrangement, exterting a force on said fin in a direction transverse the longitudinal axis of the slot to decrease the diameter of said opening until the fin tightly embraces the tubular member, and filling 3,216,095 Patented Nov. .9, 19

3 4 said slot with a metallic weld that interconnects the 2,356,779 8/44 Morrison.

spaced edges of said slot and upon cooling contracts to 2,453,567 11/48 Bronandcr 165--182 X draw said fin into closer contact with {he tub'ul ar member. 2,468,503 4/49 Lister 29-447 X 4 i 2,574,142 11/51 Buongirno 29-1573 X References Cited by the Examiner 5 3,158,352 7 11/ 64 Grove.

UNITED STATESPATENTS FOREIGN A S 4 0, 1 11/90 Weisel- 1 725,382 3/55 Great Britain. 1,775,706 I 9/30 Trane. 2,219,085 10/40 Watson. 10 WHITMORE A. WILTZ, Primary Examiner. 

1. THE METHOD OF SECURING AN EXTENDED SURFACE FIN TO THE OUTER SURFACE OF A TUBULAR MEMBER THAT COMPRISES THE STEPS OF FORMING AN OPENING IN SAID FIN SLIGHTLY LARGER THAN THE OUTER DIMENSIONS OF SAID TUBULAR MEMBER, FORMING A RADIAL SLOT IN SAID FIN EXZTENDING FROM SAID OPENING TO OUTER PERIPHERY, INSERTING SAID TUBULAR MEMBER INTO THE OPENING IN SAID EXTENDED SURFACE, EXERTING A FORCE ON SAID FIN TENDING TO CLOSE THE SLOT AND SIMULTANEOUSLY FILLING EACH SLOT WITH A MOLTEN METALLIC MATERIAL THAT BONDS ITSELF TO THE SPACE EDGES OF SAID SLOT AND UPON COOLING SOLIDIFIES AND CONTRACTS TO DRAW THE EDGES OF SAID SLOT INTO A MUTUALLY CLOSER RELATIONSHIP WHEREBY THE OPENING IN SAID TIN TIGHTLY EMBRACES THE OUTER SURFACE OF THE TUBULAR MEMBER. 